The present invention relates to a multiple-eye type dose distribution measuring method capable of grasping a three-dimensional form of an object to be measured or remotely evaluating a three-dimensional dose distribution by using a multiple-eye type radiation meter probe.
The conventional radiation meter probe used in radiation measurement is so-called a single-eye type radiation meter probe having a single radiation detector to measure only a dose distribution on a surface of an object to be measured. Consequently, in the case where the object to be measured is a planar surface (two-dimensional surface), the dose distribution can be determined by measuring the surface at a multiplicity of points and transcribing the result thereof to a planar graph.
As the radiation detector main body, a scintillation detector, a semiconductor detector or the like has been generally used.
In various research facilities or nuclear reactor facilities dealing with radioactive substances, there are cases of desiring to measure a three-dimensional form or distribution of the radioactive substance. These cases include, for example, remote measurement of radioactive facilities prior to demolition thereof or dose distribution measurement of a fuel assembly. When facilities containing high-level radioactive substances are demolished, it will helpful for improving safety and efficiency, if a three-dimensional form and dose distribution of the radioactive substance can be grasped in advance. Also, it is possible to efficiently design a waste storage scheme in advance. Furthermore, if the dose distribution of equipment in nuclear facilities is grasped without demolition, maintenance scheme can be properly planned.
However, in the foregoing conventional method, it has been difficult for a solid (three-dimensional) object to be measured to grasp a three-dimensional shape thereof. Moreover, in the conventional measuring method, it has been impossible to measure a shape or dose distribution of a radioactive substance contained within a vessel. Thus, it is impossible to cope with the desire to measure a three-dimensional form or dose distribution of the radioactive substance as described above.
It is an object of the present invention to provide a multiple-eye type dose distribution measuring method capable of grasping a three-dimensional form of an object to be measured or evaluating a three-dimensional dose distribution thereof.
According to the present invention, there is provided a multiple-eye type dose distribution measuring method comprising providing a multiple-eye type radiation meter probe in which at least two directional radiation detectors are arranged so as to be spaced from each other and directed toward a point to be measured; and carrying out dose measurement by directing the radiation meter probe toward Man object to be measured from different positions to thereby determine a three-dimensional dose distribution of said object to be measured.
The radiation detector preferably used in the present invention has a structure in which a periphery of the radiation detector main body, except for a detection surface thereof, is surrounded by a radiation shield to reduce the effect of radiation from other than the object to be measured and from Compton scattering. The multiple-eye type radiation meter probe preferably has a structure in which a holding angle of the radiation meter probe is changeable so as to have a shortest distance to the point to be measured. It is preferable to use a radiation meter probe in which two radiation detectors are arranged to be movable and changeable in their setting angle so that the point to be measured and two detectors are positioned at vertexes of an equilateral triangle or an isosceles triangle. By using such a radiation meter probe, later analytic operations are facilitated.